The 24-year-old was forced off shortly before half-time after opening the scoring for United to equalise in a hectic first 34 minutes at the Madejski Stadium.

The Red Devils' medical staff assessed the injury on Sunday and discovered a partial tear of his hamstring but were expecting worse after Anderson complained of pain in his groin and abductor. He will undergo further scans on Monday before beginning his rest and rehabilitation.

The midfielder has featured in each of United's last eight games after seeing a resurgence in his form and has impressed Sir Alex Ferguson to ease doubts over his future at the club earlier this season.

"He's been playing really well and scored a great goal today," Sir Alex told MUTV following the victory, which moved United back above Manchester City at the top of the Premier League table. "I'm very disappointed for him."

The news comes as a blow to United ahead of their final Champions League group clash with Cluj on Wednesday and Sunday's Manchester derby, with Shinji Kagawa and Nani both at least a fortnight away from a first-team return.